Adjustable countersink or the like



July 25, 1944-. HOTCHNER 2,354,461

ADJUSTABLE COUNTERSINK OR THE LIKE Filed Jan. 21, 1943 INVENTOR.

Patented July 25, 1944 UNITED STATES PATENT OFF CE Application January 21, 1943, Serial No. 473,145

6 Claims.

This invention relates to a countersink or the like having removable bits which may be quickly adjusted so as to countersink holes to any of a wide range of angles,andwhich maybe quickly removed for resharpening or replacement by other bits ground for variousspecial purposes such as spot facing, end milling, reaming or counterboring. For general shop use the tool is suitable as a common countersink with cutting edges extending close to the tool axis and capable of chamfering holes of any size up to its extreme capacity for any given angle. It may as well be used as a pilot countersink for specific diameters of holes by the insertion of bits ground for the purpose.

It is an object hereof to produce a simple, rugged tool which may be manufactured to a high degree of tolerance at moderate cost, which will retain its accuracy over a practically indefinite life, and be capable of accurate setting and adjustment by mechanics of ordinary skill.

As embodied in anadjustable countersink, in which form the invention is shown in detail in the accompanying drawing, it is an object to provide a tool, which as a single tool with a selection of bits in a shop, will take the place of not only the variety of countersinks ordinarily kept on hand to chamfer holes at different angles, but serve as a general utility tool of numerous applications.

It is a further object to produce a tool having means to hold the bits by broad surface contact firmly wedged in cavities without any chance. of play, and backed up close to the cutting edges by substantial masses of metal delivering driving force through the shortest dimension of the bits to the cut surface, in order to minimize the strain on the bits and any tendency to chatter by resilience in any part of the tool.

Another object is to produce a tool of the character described which, whether used as a pilot toolor otherwise will have a properly contoured cutting edge with ample chip clearance and substantial backing up to the innermost diameter of the Work, and further capable of repeated resharpening withoutdetracting from these imparent in the following specification taken together with the drawing in which I show my tool in certain preferred embodiments thereof. It is to be understood however, thatthis invention is not limited to the forms shown but may be vari-. ously embodied in a cutting tool in various modifications of its different features within the purview of the appended claims, the terms: of: which are to be read as embracing all substantial equivae lents thereof. a In the drawing the same reference numeral indicates the same or the equivalent part throughout. Figure 1 is an elevation of atool-provided with straight edge bits Without pilots .The, bits are shown set at 45 as an average angle of cut for general use. Figure 2 is an end-viewof thetool in conventional projection from Figure 11:

Figure 3 is a sectional view of the tool. from the same direction of view as thatof Figure .1 .and taken as indicated by thesection line 3-3 in Figure 2. Figures 4 and 5 are sectional viewsof the same taken as indicated by the section lines 4-4 and 55 in Figure 1. v In Figure 6 I show a crosssectionthrough the bit and the immediately associated elements of the holder showing the manner in which the ,bit is pressed home in its recess in the head. .The axis of the bit is shown by the line and broken lines a continuation of the solid of revolution of which the bit is a segment. Takeninconnection with the three axes similarly marked shown in Figure 2, and the line X" -X in Figure 1, representing the plane in which these axes lie, the degree of freedom of the bits is defined. ,This View is taken along section line 6-6 in Figure 3.

Figure 7 is a perspective View of the bitfshowing by broken lines a continuation of the solid of revolution of which it is a segment and also showing the bit axis v f Figures 8 and 9 illustrate thesetting of the bits to difierent angles of countersink.

Figures 10 to 13 show the contouring of special bits for various special purposes and especially the contouring of bits for pilot .control operations.

having a central locking rod.

The tool comprises a holder, indicated by nu-- freedom for adjustment and lock them in a given position within such restraint for cutting service.

Figure 14 is a sectional View ofa modified form of the tool in which the holder is a single piece Each bit is a segment of a solid of revolution having a cutting edge along a chord of the circle of one side of this solid, and is retained in the holder in a cavity having a pair of opposing main walls of similar contour.

As seen in the perspective view of Figure 7 and the cross section of Figure 6 this solid of revolution is a disk having one flat and one concave side. The bit therefore has one flat side, indicated by numeral 6. The cutting edge I is along a chord of this side. The other sid 5 of the bit converges to the side 6 from the rim I toward the axis X-X. The clearance surface 8 is ground backward away from the cutting edge, being somewhat steeper toward the corner 9 which is the central edge of the bit as it is set in the holder. For the sake of cutting edge formation the rim l0 may be perpendicular to the side 6. However, in designing tools favor may be given the feature of the contact between the bits and the locking wedge at the expense of other features of the tool if found desirable.

Various constructions may be employed in the holder. The most simple construction is that shown in the drawing in which the bits are held in recesses cut into the solid material of the holder, the walls of the recesses being complementary to the surfaces of the bits. Thus, since the sides of the bits converge toward the bit axes they cannot move out of the recesses radially but must be rotated around their axes to admit, adjust or remove them from the holder. To look them in position means are provided to force them outward against the walls of the recesses thus bringing into play a frictional engagement which holds them firmly 'in position against all working forces. Furthermore the mass of the bits and'the; holder head are combined as one solid body effective close to the bit heels to back up the cutting edge with the minimum of stress in the bits. This makes it quite practicable to use the more brittle cutting materials such as the carbides which take heavy cuts at high speed but do not withstand internal stress when unsupported against the reaction of the work.

InFigure- 6 a section through the bit is shown, the remainder of the solid of revolution of which it is a part being shown in broken lines. The floit can only move, when in the holder, by rotation around the axis XX as shown. The wall of the recess contacting side of the bit is indicated by numeral l2 and the edge of this wall by l3 in Figures 1 and 2. Likewise the opposite wall contacting side 6 of the bit is indicated by M and its edge by 15 in Figures 1 and 2. The recesses may be cut to a high degree of accuracy on a milling machine so that the bits will, if manufactured to a uniform size, fit with but a few thousandths of an inch play and be freely interchangeable in the different recesses. The edge of the bit will be pressed away from. its mating surface in the recess a very slight amount, usually insufiicient to be noticeable, and hence nospace is shown between them in the drawing.

In Figure. 1, the line X-X indicates the plane in which all of the axes of the bits lie. In Figure 2 the axes of the bits are shown tangent to a circle in broken line. .This defines the bits as similarly spaced lengthwise with the tool axis Y-Y, to have the same lead into work, and parallel thereto. It will !be seen that the face 6 of each bit is in line with the tool axis. Therefore a protractor laid along the side of the holder will give a direct gauge of the bit angle, affording a very convenient means of setting the tool.

In Figures 2 and 3 we see that the points I6 of the bits come very close to the tool center so that the tool may be used in all sizes of holes from a very small size up to its maximum capacity. In Figures 8 and 9 it is shown that the variation of the minimum size of hole is very slight even for extreme adjustments of the tool.

To look the bits in position I provide a wedge member and means to press it forcefully against the edges 29 of the bits. The wedge should be free to shift radially so that it will equalize the pressure between the bits. To carry this feature out, the preferred construction is to drill a hole through the holder from the opposite end, insert the wedge and back it up with a screw. In the tool of Figures 1 to 13 the holder is in two pieces. The head has the hole l8 drilled into it until it opens up through the recesses sufficient to allow a small portion of the back of each bit to be exposed in the hole as indicated by l9. The end' of the hole is tapped at 20 to receive the threaded end 2| of the shank 22. The holder is cut to a hexagon at 23 and the shank carries a hexagon shoulder at 24 for the reception of the jaws of wrenches to tighten the tool.

Th end of the shank has a center hole 21. The wedge plug 25 has a pointed end 26 fitting into this hole. The plug is slightly less in diameter than the bore of the hole so that it can rock sufficient to equalize the pressure between the bits. The end 28 is contoured to fit the edges 29 of the bits. As will be seen in Figure 6, if this edge is a sharp corner, the contact between bit and wedge will be a line contact. If the bit he made of. brittle material it may be necessary to shape the bit edges to provide a surface contact with the wedges at a slight expense to the feature of a well pointed tool to work in small holes.

In setting the tool, the wedge is loosened just sufficient to permit the bits to be moved by lightly tapping on one end or the other of the back of the clearance surface. By means of a protractor along the edge of the holder the angle is gauged until all of the bits'are at the desired angle and then the Wedge is tightened by screwing up the shank. Another convenient method of setting the tool is to make a taper gauge by turning out a block of metal to the desired angle and setting the bits by holding the tool in its proper position in the hole, pressing the bits against the tapered surfaces and tightening them in place. The bits may be given any desired rake by grinding backward on the surface 6 and the clearance modified according to the usual practices, advantage being taken of the ample chip clearance space to attain a better tool formation at the point of the tool than that which may be had with the fixed countersinks of the prior art. It is particularly to be noted that the invention is not limited to the particular concave radial section of bit which I have shown with the correspondingly tapered slot section. I have shown this as my preferred contour because the wedging of bits of this section into the recess shown has the effect of forming a solid mass of each bit and the boss I1 behind it up to the heel of the cutting edge, forming a very desirable tool feature. Various other contours, such as L slots or T slots may be used for special purposes.

Figures 8 and 9 show two extreme angles for countersinking. It is seen that the bits are well backed up over the extent of the cutting edges where the heaviest service is met for the range of an'gles metfin general shop practice. Iti's {02bvi'ousth'at for-special service'theboritoiir of the holder may be modified t'o increase-this "backing at one 'regiono'r the othe" ndthat the material "of the head in front oftherac stithe hits my be cut away to improve chip clearance if desired.

The provision of pilots for countersinking or spot facing is readily had with my tool. Figures and 11 show bits ground with pilot shoulders 35. In Figure 10 a pilot countersink is shown and in Figure 11 a counterbore. In these views and also in Figures 12 and 13 I have shown in broken lines the position taken by the bits in their sweeparound the tool axis for the sake of clarity. It will be seen that these pilot shoulders are the equivalent for all practical purposes of a solid pilot pin. The edges 36, obviously must be ground concentric with the tool axis. The cutting edges are indicated by 38 and the clearance by broken lines. It will be seen at 39 that the clearance undercuts the shoulder to permit of grinding the edge up to the pilot. A taper entering edge may be ground at 31 to any angle desired.

Figure 12 shows the adaptationlof the tool by suitable bits as an end mill and Figure 13 as reamer.

Figure 14 shows a construction in which the holder is in one piece with a central locking rod. The holder 40 has recesses cut in the head as described above and the hole 42 is drilled up to and opening into these recesses. The locking rod 4| is threaded in the threaded end 43 of theholder and has a hexagon head 44 for tightening with a wrench. The opposite end 45 of the rod is contoured to fit the edges of the bit. The rod should be slightly smaller in diameter than the bore of the hole and be resilient enough to equalize the pressure between the bits by springing the maximum displacement from the axis which any inequality in construction might produce.

The novel features of-thisv invention may be applied to cutting tools of various types other than the general class embracing those specifically described above.

The term concave descriptive of the contour of the bits as used in the claims is embracive of special formations such as those presented by T or L sections.

Having thus described claim is: I I

1. Acountersink comprising: an arbor having my invention, what I a plurality of cavities opening to the leading nd radius approximating that of the cavity rim walls, said circle lying in a plane perpendicular to the arbor'axis being concentric with the same and slightly forward of the leading end of the arbor, one side wall of each cavity being convergent at least in part toward the other wall from the rim toward the cavity axis so that a solid of revolution of surfaces complementary to the said cavity walls may turn in any of said cavities around the cavity axis but may not move radially outward therefrom, the leading one of the walls of each of said cavities in the direction in which the tool turns in use being parallel to and radiating from the arbor axis, there being an, axial opening in said arbor from the trailing end thereof to and opening into each of said cavities through the rim walls thereof, a bit in each of said cavities comprising a segmentary portion of "a solid "of revolution of surfaces jc ompleme cavities, a wedge memberinsaid axial o'p ng in to the cavity walls and having awor m e gfe along a chord of'the side corresponding tojth'e leading wall above described :of the' r'esp'ctive said'arbor bearing on theriinso fgsaidbi wh they are exposed through'the' rim of their respective cavities, and means to force said wedge member against said bits to lock them in their set positions.

2. A device as set forth in claim 1 in which the cavities and the bits are respectively three in number and said wedge member equalizes its pressure between the bits to automatically compensate for irregularities in construction and those caused by wear and foreign matter.

3. A countersink comprising: an arbor having a plurality of cavities opening to the leading end thereof, each of which cavities has a pair of opposing side walls and an arcuate rim wall all concentric and symmetric around an axial line, all of which axial lines are tangent to a circle of radius approximating that of the cavity rim wallssaid circle lying in a plane perpendicular to the arbor axis being concentric with the same and slightly forward of the leading end of the arbor, one side wall of each cavity being convergent at least in part toward the other wall from the rim toward the cavity axis so that a solid of revolution of surfaces complementary to the said cavity walls may turn in any of said cavities around the cavity axis but may not move radially outward therefrom, the leading one of the walls of each of said cavities in the direction in which the tool turns in use being parallel to and radiating from the arbor axis-there being an axial openingin said arbor from the trailing end thereof to and'opening into each of said cavities through the rim walls thereof, a bit in each of said cavities comprising-a segmentary portion of a solid of revolution of surfaces complementary to the cavity walls and having a working edge along a chord of the side corresponding to the leading cavity wall of the respective cavities, and a locking member for said bits extendin through said axial openingin said arbor bearingon the rims of said bits where they are exposed trough the rim walls of their respective cavities and'adapted to be driven thereagainst to lock the bits in their set positions. I

4. A device as set forth in claim 3 in which the cavities and the bits are respectively three in number and said locking member is adapted to equalize the pressure from one bit to the other to compensate for irregularities in its bearing thereagainst.

5. A countersink comprising: an arbor having a plurality of cavities opening to the leading end thereof, each of which cavities has a pair of opposing sidewalls and an arcuate rim wallall concentric and symmetric around an axial line, all of which axial lines are tangent to a circle'lying in a plane perpendicular to the arbor axis and slightly forward of the leading end of the arbor, one side wall of each cavity being convergent at least in part toward the other wall from the rim toward the cavity axis so that a solid of revolution of surfaces complementary to the said cavity w'all openings I prising a segmentary portion of a solid of revolution of surfaces complementary to the :cavity walls and having a working edge lying along a chord of one side, and a locking member extending through said axial opening in said arbor bearing on the rims of said bits where they are exposed through the rim wall openings of their respective cavities and adapted to be driven thereagainst to lock the bits. in their set positions.

6. A device as setforth in claim 5 in which the 

